1. Field
The present disclosure relates to ferritic/martensitic oxide dispersion strengthened steel with enhanced creep resistance and a method of manufacturing the same.
2. Discussion of Related Art
An iron (Fe)-chromium (Cr) alloy in which chromium is added to iron at 8 to 12 wt % is generally normalized and tempered, thereby forming a tempered martensite structure. Such a high chrome alloy is used as a material for a structural component of a nuclear power system such as sodium-cooled fast reactor or a thermoelectric power plant due to excellent neutron radiation resistance at a high temperature and an excellent mechanical property. However, there is a limit to a temperature at which the alloy is used as a structural material due to drastic reduction in tensile stress and creep strength at a high temperature such as 600° C. or more. Alternatively, oxide dispersion strengthened steel with an enhanced mechanical property at a high temperature by dispersing an oxide in an alloy matrix is being developed. Oxide dispersion strengthened steel is an alloy in which a nano oxide with excellent thermal stability such as yttria (Y2O3) is uniformly dispersed in an iron (Fe)-chromium (Cr)-based alloy matrix, which is enhanced in high temperature mechanical property such as a creep strength, compared to a general alloy, due to dispersion strengthening of an oxide as well as solid solution strengthening of a matrix structure.
Generally, oxide dispersion strengthened steel has excellent high temperature strength compared to a general alloy, but a condition for designing was not still sufficiently satisfied. To improve such a problem, an alloy atom such as tungsten (W), tantalum (Ta), or niobium (Nb) is added to an iron (Fe)-chromium (Cr)-yttria (Y2O3)-based alloy. However, when oxide dispersion strengthened steel in which tungsten (W) is added as a solid solution strengthening element is used under a high temperature stress atmosphere for a long time, a Laves phase such as brittle (Fe,Cr)2W is produced, and thus a long-term creep characteristic is considerably decreased.